The subject matter disclosed herein relates to climate control systems. More specifically, the subject disclosure relates to crank case heater operation for packaged air conditioning units.
Compressors are utilized in heating, cooling and refrigeration applications. These compressors require oil or other lubricant to lubricate moving parts of the compressor. The oil is housed in a crank case from where it is drawn into moving parts of the compressor. During normal operation of the refrigeration circuit, operating pressures and temperatures tend to keep the oil free from liquid refrigerant. When the compressor is not operating, however, refrigerant in the system tends to migrate to and condense in the coldest parts of the system, one of which is often the compressor crank case. Under such conditions, there is a danger that the crank case oil will be diluted with refrigerant reducing its viscosity to the point where if the compressor is then restarted, damage may occur. Crank case heaters are utilized to boil off the refrigerant from the crank case and to prevent migration of the refrigerant thereto.
Many packaged air conditioning units, such as those servicing large buildings or spaces, include multiple interlinked air conditioning circuits. Each circuit may include at least one compressor, at least one condenser, at least one evaporator, and at least one expansion valve. Each compressor in the air conditioning unit has a crank case heater connected to it to boil off liquid refrigerant when the compressor is in “off” mode.
In some environments, the compressors operate mostly on a seasonal basis, during which the compressors may sit idle for extended time periods, for example 3 to 6 months at a time. In current systems, the crank case heater for each compressor is then in operation for the entire time the compressors are idle to boil off the liquid refrigerant. This results in substantial energy usage by the crank case heaters.